The present invention relates generally to airfoils and more particularly to a stack of clear laminated removable lens for reducing surface drag on airfoils while allowing for the viewing of advertising graphics on the airfoils.
Face shields are employed in environments where contamination of the eyes may occur. It is well known in the art that flexible transparent lenses affixed by numerous methods are overlaid on the face shield for protection. The lenses are easily removed and discarded when visibility is reduced from the accumulation of dirt or other contaminants. In motor sports for instance, multiple layers of transparent lenses are overlaid on the face shield, each being sequentially removed as they become contaminated, because they reduce the visibility of the operator. The drawback of the lenses in the prior art is that each transparent lens applied over the face shield is itself a hindrance to good visibility due to its optical index of refraction. Most common materials used as plastics have optical indexes of refraction ranging from 1.47 to 1.498. The index mismatch between the removable lens and air (air has an optical index of 1.00) causes a reflection of 4% of the light that would normally come to the operator's eyes. This reflection effect is additive for each additional surface to air interface. Then for each removable lens having two surfaces, the reflections are 8%. Thus a stack of seven lenses would reflect 42% of the light away from the operator thereby reducing the brightness of the objects viewed. A second optical phenomenon occurs simultaneously that also reduces visibility. The reflections are bi-directional and thus make the lens stack appear as a semi-permeable mirror to the operator. This mirror effect further reduces visibility, because the light that passes through the lens stack reflects off of the operator's face and then reflects off of the lens stack into the operator's eyes. The effect to the operator is that he sees his own image on the inside of the stack nearly as brightly as the objects viewed on the outside. This significantly reduces visibility.
Another drawback to this stacking arrangement is that moisture exhaled by the operator's breath can cloud or fog-up the lenses also reducing visibility. The air spaces between each lens allow the moisture to enter this area.
Airfoils are commonly used on racecars to create down force which improves the traction of the car. In dirt car racing, the airfoil can be as large as sixteen square feet. Most of this area is covered with advertising graphics.
As described above, dirt and mud accumulate on a driver's goggles during a race is a significant problem. Such an accumulation of dirt and mud is not limited to a driver's goggles. The dirt and mud accumulates over the entire vehicle. Such an accumulation of dirt and mud can be a particular problem on airfoils. The airfoils accumulate heavy mud and dirt which both reduces the efficiency of the airfoils and covers up the advertising graphics on the airfoils. Another drawback of current airfoils is drag that is created by the airfoil shape, attitude and the surface finish of the airfoil. Part of this surface drag problem is created by imperfections in the airfoil such as rivets and joints.
Therefore, there is a need for a way to quickly clean accumulated mud and dirt from an airfoil so as to reduce the surface drag caused by the accumulated mud and dirt as well as to allow for the viewing of any advertising graphics on the airfoil.